Body/frame advice request 73 Blazer, more than I wish I had to do

[catdaddy]

I posted this elsewhere - but this looks like a more active place to ask..

My first car was a 73 Blazer 4x4. in the early 90's I mildly restored/updated it, rebuilt everything etc.
Somehow it survived my marriage. It wasn't practical for a young family, it spilled oil. (believe me, my wife tried to make me sell it and I'm still married to her) I was able to hide the truck out of sight for years.
The next time the truck came up, I had the brilliant idea to say the truck was going to be for my son.
One day, Texas happened.
I let my father take the truck out to South Texas when he retired. He was/is a master mechanic and experienced collision expert. The idea was that I would move there (I did, for a bit) and bring the truck back to road-ready condition, it still ran great but had things that needed doing.
Fast forward 10 years and the warm salt air has cannibalized the body. I haven't been down there to visit, but I know my father doesn't want me to see it. It's mine though and I promised it to my son so I have to do some major work.
TLDR: I need a new body and I would like to do it as cheaply as possible - so I'm looking at available K5 bodies and the most intact I can find are 80's K5.
I know there are differences - the door posts will have to be cut, along with the windshield frame, etc. There's also the gas door thing.
I'm wondering if anyone has done this before?
My father insists that he once measured an 87 Suburban and that chassis was narrower than the one in his 74 Suburban (He was looking at a potential swap and EFI, etc). I found aftermarket replacement frames for K5 and there is nothing that I could find about these differences.
I don't have long to get this truck ready, my son just turned 14 - your help is appreciated.
Thanks..